<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="./vue.js"></script>
</head>
<body>
    <div id="app">
        <div>{{a}}</div>
        <div>{{obj.b}}</div>
    </div>
    <script>
        var vm = new Vue({
            el:'#app',
            data:{
                a:'我是根级响应式属性a',
                obj:{}
            }
        });
        Vue.set(vm.obj,'b','我是VUE SET添加的响应式属性VM OBJ');
    </script>
</body>
</html>